RU2321866C1 - Method for diagnostics of circuits of arc-suppressing contacts of regulators under load of rnta type - Google Patents

Abstract

FIELD: diagnostics of power transformers, namely circuits of arc-suppressing contacts with current-limiting resistance of fast action regulator under load, wherein selector, contactor and drive mechanism are combined in a single block, and transformer windings are coupled in a star.

SUBSTANCE: diagnostics is performed by comparing current oscilloscope patterns to analogical oscilloscope patterns, made during pre-commissioning tests during switching of selector from one position to another without opening the tank of regulator under load and draining transformer oil of contact system of regulator under load simultaneously of all three phases. Oscilloscope recording is performed according to a circuit which includes inductivity of winding of power transformer relatively to contacts of high voltage winding and the neutral. Time constants of transfer process of current alteration are compared in case of its drop. Disruption of contact system of arc-suppressing contacts is characterized by increase of time constant compared to pre-commissioning tests, and presence of coil shorting in current-limiting resistance is characterized by reduction of the constant. Tear of current-limiting resistance is characterized by time constant equal to zero.

EFFECT: prevented pollution of environment, reduced working hours, possible diagnosing under any weather conditions.

4 dwg

Description

Technical field

The invention relates to methods for diagnosing power transformers in the electric power industry, namely to diagnosing circuits of arcing contacts of high-speed regulators under load (on-load tap-changer) without draining transformer oil and opening the tank, in which the selector, contactor and drive mechanism are made in a single unit, and the transformer windings are connected in a star.

It can be used in the energy sector for complex inspections of power transformers, commissioning, preventive, periodic tests to diagnose on-load tap-changer malfunctions, for example, devices such as РНТА-35/200, etc.

A method for diagnosing on-load tap-changer circuits of an on-load tap-changer involves analyzing the oscillogram current curve to simultaneously determine the integrity of current-limiting resistances installed in three phases, as well as to identify the coil circuit and violation of the contact system in the circuits of the regulator's arcing contacts.

State of the art

A known method for determining the resistance value by the bridge method. Typically, the measurement of current-limiting resistances of the regulator in order to determine their integrity using this method can only be performed after draining the transformer oil and opening the tank, since current-limiting resistances are inside the tank of the regulator [Factory documentation of the Togliatti Transformer Plant. "The device for regulating the voltage of power transformers under load type RNTA-Y-35 / 200R-16 / 20-93U1." Operation manual 674261.023RE)].

There is also a method of determining DC resistance by the method of "voltmeter-ammeter". [G.V. Aleksenko, A.K. Ashryatov and E.S. Frid. Testing of high-voltage and powerful transformers and autotransformers, part II, M.-L .: Gosenergoizdat, 1962, 832 p. with hell. (in the Transformers series, issue 9). Collection of teaching aids for monitoring the state of electrical equipment. Section 2. Methods for monitoring the status of power transformers, autotransformers, shunt and arc suppression reactors. Moscow, ORGRES, 1997, S.100]. As a resistance meter in this device, a voltmeter and an ammeter are used.

To determine the integrity of the active resistances, the presence or absence of coil faults in them, and the absence of defects in the transient resistances of the contact system using this method, it is also necessary to drain the transformer oil and open the on-load tap-changer.

SUMMARY OF THE INVENTION

The main objective of the invention is the creation of a method for all-weather diagnosing the integrity of current-limiting resistances, monitoring the transient resistance in the contact system of each phase without opening the on-load tap-changer and draining the transformer oil, eliminating the possibility of environmental pollution, reducing labor costs during its implementation and the ability to evaluate the above parameters under any weather conditions .

The problem is solved due to the fact that in the proposed method, the diagnosis of circuits of arcing contacts is performed by comparing current waveforms with similar waveforms performed during commissioning tests when the selector is switched from one corresponding position to another without opening the on-load tap-changer and draining the transformer oil of the on-load tap-changer system at the same time three phases according to the circuit, including the inductance of the winding of the power transformer relative to the terminals of the high voltage winding and neutrality, while the diagnostics of current-limiting resistances in each phase of a three-phase power transformer, in which the selector, contactor and drive mechanism are made in a single unit, is performed by the value of the time constant (τ) of the transition process of current change during its decline, and violation of the contact system of arcing of the contacts is characterized by an increase, by the presence of a short circuit in current-limiting resistances - a decrease in the time constant (τ) from commissioning tests, while the breakage t koogranichivayuschego resistance corresponds to the time constant (τ), is equal to zero.

Description of figures.

For the diagnosis of arcing contacts circuits - 19 on-load tap-changers of the РНТА type - 35/200 of the Togliatti Transformer Plant, Fig. 1 shows the connection diagram of the digital recorder 15 to the terminals of the winding of the high-voltage transformer 10 using a four-wire cable 14. Digital recorder 15, which has three measuring current sensors ( IDT), is powered by a three-channel DC voltage source 16. The РНТА - 35/200 on-load tap-changer has a single drive (not shown) and all three phases of the controller (11, 12, 13) are in a separate tank filled with transformer aslom. This type of regulator differs from other high-speed on-load tap-changers in that the selector, contactor, and drive mechanism of all three phases are made in a single unit, i.e. the contacts of the selector and the contactor are in the same tank, and the drive is installed on its cover. Figure 1 shows the current-limiting resistance 17, the main 18 and the arrester 19 contacts installed in phase "A".

Figure 2 shows the real waveforms of currents obtained on three phases of the on-load tap-changer type RNTA-35/200 using a three-channel digital recorder.

Figure 3 shows the operating procedure of the main 18 and arrester 19 contacts of the switching device when transferring from the first to the second position.

Figure 4 presents the types of current waveforms for various defects in the circuit of the arrester contact of the on-load tap-changer of the type РНТА - 35/200.

Disclosure of invention

For the diagnosis of circuits of arcing contacts - 19 on-load tap-changers (11, 12, 13) with current-limiting resistance (17), a three-phase power transformer 10, in which the selector, contactor and drive mechanism are made in a single unit, the currents are oscillographed according to the circuit shown in FIG. 1, using a digital recorder 15 using a three-channel DC voltage source 16 and a four-wire cable 14 (FIG. 1).

Figure 2 presents the waveforms of the currents of all three phases of the on-load tap-changer obtained on the regulator type RNTA-35/200, and figure 3 - the operation of the main 18 and the arcing contacts 19 of the switching device when transferring from the first to the second position. It can be seen that until time t ₁ (figure 2) the position of the main 18 and arrester 19 contacts correspond to the state depicted in figure 3, a and figure 3, b. The movement of the main 18 and the arrester 19 contacts shown in figv, will correspond to the period of time starting from t ₁ to t ₂ (figure 2). After time t ₂ (figure 2), the position of the main 18 and arcing 19 contacts corresponds to the state shown in figure 3,

Figure 4 presents high-quality oscillograms of the curves of currents of on-load tap-changers of the РНТА-35/200 type with various defects in the circuit (from point D to point E) of the arrester contact (Fig. 3). In particular, in figure 4, in the subgroup "a" shows the waveform of the current of one phase of a faultless on-load tap-changer. If there is a defect in the contact system of the arcing contact (the transition resistance exceeds the data measured at the factory or the data of previous measurements), it is obvious that the time constant (τ) will exceed the initial value obtained during commissioning tests of the equipment or from the data of previous measurements (Fig.4b )

In the case of a short circuit at the current-limiting resistance 17 (Fig. 3), the time constant (τ) will sharply change in the direction of decrease and the shape of the current curve (i) will look like that shown in Fig. 4c. Of course, when the current-limiting resistance 17 is broken, the time constant (τ) will be zero and the shape of the current curve will have the form, as shown in Fig. 4d.

Thus, by analyzing the oscillogram current curve of the operation of the arcing contacts 19 by comparing the oscillograms with similar oscillograms obtained during commissioning when switching the regulator from one corresponding position to another, it is possible to diagnose arcing contact circuits in each phase of the РТА-35/200 on-load tap-changer production of the Togliatti Transformer Plant.

The main advantages of the proposed method are: reducing material costs and diagnostic time, eliminating the likelihood of contamination of the dielectric fluid and the environment, the ability to control current-limiting resistances without opening the on-load tap-changer and draining the transformer oil, which can be done under any environmental conditions.

Figure 1 - Connection diagram of a digital recorder for the diagnosis of circuits of arrester contacts on-load tap-changer type RNTA

1-9 switch branch numbers; 10 - power transformer; 11 ÷ 13 on-load tap-changer of phases “A”; "AT"; "C", respectively, where 17 is the current-limiting resistance; 18 - main contact; 19 - arcing contact; 14 - four-wire cable; 15 - digital recorder, where IDT - measuring current sensors; 16 - three-channel source of constant voltage.

Figure 2 - Oscillograms of the currents of the arrester contacts of the RPN type RNTA-35/200 (plant No. 44) of the transformer T-2 type TRDN-25000/110 (factory number 23077) installed on the station. Zapadnaya Northern electric networks of Chuvashenergo OJSC (without oil drain and without opening the on-load tap-changer tank).

Figure 3 - The operation of the main and arcing contacts of the device type RNTA-35/200 when moving from the first to the second position.

1, 2, 3 - numbers of branches of the voter; 17 - current limiting resistance; 18 - main contact; 19 - arcing contact.

a - the initial first position of the on-load tap-changer;

b - scheme of the "bridge";

c - a circuit in which the current passes only through the arcing contacts;

g - the initial second position of the on-load tap-changer.

Figure 4 - An indicative view of the waveforms of the current for various defects in the circuit of the arrester contact of the on-load tap-changer type РНТА - 35/200:

a) - there are no defects in the contact system;

b) - the presence of a defect in the contact system;

c) - coil circuit of current-limiting resistance;

d) - breakage of current-limiting resistance.

Claims (1)

A method for diagnosing circuits of arcing contacts of a regulator under load (on-load tap-changer) with current-limiting resistances of a power three-phase transformer, in which the selector, contactor and drive mechanism are made in a single unit, and the transformer windings are connected to a star, characterized in that the diagnostics are performed by comparing current waveforms with similar oscillograms performed during commissioning tests when switching the selector from one corresponding position to another without opening the tank P Н and the drain of transformer oil of the on-load tap-changer contact system at the same time of all three phases according to the circuit, including the inductance of the power transformer winding relative to the terminals of the high-voltage and neutral windings, while the time constants of the transient current change during its decline are compared, moreover, violation of the contact system of the arcing contacts is characterized by an increase, and the presence of a short circuit in the current-limiting resistance - a decrease in the time constant from commissioning tests, while In current limiting resistance there corresponds a time constant equal to zero.

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